Declaring Functions using NSArray as an Arguments

Question

I have a function as follows:

-(int)ladderCalc:(NSArray*)amounts percentages:(NSArray*)percentages amount:(int)amount
{

   // Do some stuff

   return foo;
}

I have declared like this in the header file:

-(int)ladderCalc:(NSArray*)amounts percentages:(NSArray*)percentages amount:(int)amount;

But I am getting an error "implicit declaration of function is invalid in c99" when I try to use the int value returned elsewhere in the same file. Am I not declaring the function correctly?

UPDATE

I am realizing that I am not declaring this in the standardized way, I changed my declaration to MarkGranoff's recommendation (see the changes above) but I am still getting it as a warning this time.

Here is the context of how I am calling this function:

-(int)fooTotal: (int)amount 
{

   int totalFee = 0;

   // Declare arguments
   NSArray *percentages = [[NSArray alloc] initWithObjects:firstValue, secondValue, thirdValue, fourthValue, fifthValue, nil];
   NSArray *amounts = [[NSArray alloc] initWithObjects:sixthValue, seventhValue, eigthValue, ninthValue, nil];

   totalFee = ladderCalc(amounts,percentages,amount);

   return totalFee;
}

So, I am still getting a warning even though this seems to make sense as far as Obj-C style is concerned.

I am pretty sure I am not calling this function correctly, I am getting an unrecognized symbol error when I compile the project.

Undefined symbols for architecture i386:
  "_ladderCalc", referenced from:
      -[FeeCalcLibrary getMFModelTotal:] in FeeCalcLibrary-A83D2A7637F57664.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Your code has non-idiomatic spacing and no parameter names - what's up with that? — Carl Norum
– Carl Norum, Commented Nov 16, 2011 at 21:53
your definition looks weird... It should be like - (int) ladderCalc: (NSArray )array1 amounts:(NSArray)amounts percentages:(NSArray *)percentages amount:(int)amount; — Shai Mishali
– Shai Mishali, Commented Nov 16, 2011 at 21:53
I agree with the other responders that your code looks weird and that this style is generally agreed to be a bad idea in Objective-C. However, from what I can see for declaration looks valid. To determine why you are getting the error, you should probably edit your post to include the code you use to call this method. — Tim Dean
– Tim Dean, Commented Nov 16, 2011 at 22:08
@TimDean I updated my question to provide context for calling it. I also tried the first answer below and am still getting a warning. Not sure why. — Andrew Lauer Barinov
– Andrew Lauer Barinov, Commented Nov 16, 2011 at 22:26
I think I am calling this function incorrectly in the bottom code snippet of my question. Should it be done using the square bracket messaging syntax? — Andrew Lauer Barinov
– Andrew Lauer Barinov, Commented Nov 16, 2011 at 22:41

Mark Granoff · Accepted Answer · 2011-11-16 21:53:46Z

2

Try this instead:

-(int)ladderCalc:(NSArray*)amounts percentages:(NSArray*)percentages amount:(int)amount;

and change the signature of the implementation to match. Then you have arguments with names you can reference in the code of the method. Namely: amounts, percentages, and amount.

answered Nov 16, 2011 at 21:53

Mark Granoff

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2 Comments

Andrew Lauer Barinov Over a year ago

I think my problem is that I am calling it incorrectly in my code, what is the proper format for calling it?

Mark Granoff Over a year ago

Something like [myObject adderCalc:theAmounts percentages:thePtgs amount:amt].

zaph · Accepted Answer · 2011-11-16 22:23:27Z

As @MarkGranoff says.

Objective-C has it's arguments interspersed in the method name.

For the method declaration:

-(int)ladderCalcWithAmounts:(NSArray*)amounts percentages:(NSArray*)percentages amount:(int)amount;

the method name is (the colons are part of the name):

ladderCalc:percentages:amount:

Interspersed in the method name the arguments are:

(NSArray*)amounts
(NSArray*)percentages
(int)amount;

This improved readability over a "C" function call which might be:

int ladderCalcPercentagesAmount(NSArray *amounts, NSArray *percentages, amount);

Technically, Objective-C does not have named parameters, rather interspersed parameters. Named parameters tends to imply that position is not important just the associated names, an example are Python's named parameters.

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